If you work hard, it's actually probably best to give your brain a break during your free time, especially in regards to actual programming. I think it could be okay to try out some new things and read about new techniques and what not, but I don't think I'd be on fire at work if I spent my free time programming even more.
I sometimes write proof-of-concept programs at home when I really feel like it, but rarely anything more. If I have to program at home it means that I sit too much in meetings at work and my need to express myself through code is unfulfilled. That, then, means that it's time for a new job where I get to actually write programs.